Floating solar stills have long been known and typical examples are disclosed in U.S. Pat. Nos. 2,412,466 (North), 2,424,142 (Bimpson), 3,397,117 (Smith), 3,408,260 (Feldman), 3,415,719 (Telkes), and 3,703,433 (Evans). In general, floating solar stills are located on a body of water containing objectionable impurities (salt as in ocean water, various pollutants, etc.) which make it unfit for a desired purpose, such as drinking. Characteristically, such stills incorporate an enclosure in which water to be distilled lies atop a dark surface and beneath a transparent sunlight admitting sheet, such that sunlight entering through the transparent sheet is absorbed by and warms the dark surface, which warms and vaporizes the liquid.
In general, the prior solar stills disclosed in the above-listed patents are of relatively insubstantial construction to permit storage in a compact package, e.g. for emergency use at sea by shipwrecked or otherwise stranded persons. Such solar stills have typically used a plastic film envelope with sunlight admitting and absorbing portions, flotation and shaping of the apparatus being accomplished by inflation of the evaporating envelope itself or inflatable tubes formed in the walls thereof. At least in some instances water to be distilled must be added manually, on a batch-by-batch basis.
Typically, such prior devices have been intended to condense the water vapor on surfaces within the floating vaporizing envelope itself, i.e. on envelope surfaces near the relatively warm surface of the supporting body of water such that condenstaion proceeds slowly. Also, such condensing surfaces are likely to be near the contaminated liquid to be vaporized, risking contamination therefrom. In one such prior floating still, a separate condenser is located at a distance from the vaporizing chamber; however a manually operated pump is required to transfer the vapor from the evaporating chamber to the condenser.
Thus, prior devices of the type above set forth have tended to be of relatively light, delicate, collapsible construction best suited for temporary emergency use rather than in a substantially permanent installation, have tended to sacrifice efficiency for the sake of minimizing cost and maximizing collapsibility into a small space, and/or have required substantial and frequency attention by a human operator, and/or manual pumping to provide a distilled water output. Moreover, the aforementioned structures have not attempted to provide any enhancement of the local ecology, but instead are clearly directed to production of a single output, namely distilled water.
Moreover, such prior devices do not appear to attempt to tap naturally available energy sources other than the solar input used for vaporizing liquid, nor do the aforementioned patents disclose structure for using solar energy other than for vaporizing of the contaminated water.
Accordingly, the objects and purposes of this invention include provision of:
1. A floating solar still apparatus adapted to support itself upon a body of water, such as a pond, bay, etc. of salt, contaminated fresh or otherwise impure water, from which potable water is to be obtained by distillation.
2. Apparatus, as aforesaid, arranged to enhance efficiency in distillation by condensing the vaporized liquids below the thermocline in the body of water at a location well spaced below the solar heated evaporation chamber and wherein vapor is conveyed to the remote condenser without need for manual, electrical or other imported power inputs.
3. Apparatus, as aforesaid, which utilizes locally available natural energy inputs in addition to solar energy, namely wind energy, in its operation, particularly for moving vapor from the evaporating chamber to the condenser.
4. Apparatus, as aforesaid, capable of enhancing the quantity of solar energy falling on the evaporating chamber by automatic positioning of a solar reflector in at least approximate tracking relation with the sun as the latter moves across the sky.
5. Apparatus, as aforesaid, in which waste heat from the condenser is utilizable for preheating the raw liquid input to the evaporating chamber and, if desired, for upward directing of water from lower levels in the body of water to obtain other local ecology assisting products from the apparatus.
6. Apparatus, as aforesaid, which with addition of a transparent plastic film annulus extending radially between the distillation portion of the apparatus and an outer stabilizing float ring, can encourage phytoplankton activity, in terms of enhanced food and oxygen production, for enhanced growth of fish and other useful marine life in the area.
7. Apparatus, as aforesaid, which is capable of ready disassembly for maintenance and removal of precipitates, and which is intended to perform for long periods with minimal human attention in either permanent or semi-permanent location on a body of water.
8. Apparatus, as aforesaid, which without inhibiting other sunlight requiring functions, provides substantial space for support of electricity producing solar cells, e.g. to power reflector rotation, distilled water output pumping and oxygen pumping devices.
Other objects and purposes of the invention will be apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspecting the accompanying drawings.